Burner head for low calorific fuels

ABSTRACT

The burner, which comprising an air supply pipe, fuel supply pipe attached to a central burner tube, which is terminated by the front face on the side of the supply pipe whereas in the front face a support tube is fixed, on which a burner head at the burner&#39;s output is mounted, the burner head is provided with nozzles arranged in a circle near to the inner perimeter of the burner head and forming the primary stage of the burner, and further the burner head is provided with angled grooves on the outer perimeter, which form the secondary stage of the burner, and further the whirler with its inner perimeter is arranged onto central burner tube at its outlet end, and the whirler&#39;s surface has conical shape extending outwardly and the whirler&#39;s surface openings, arranged in a circle are provided.

TECHNICAL FIELD

The invention relates to combustion of low calorific fuels fromalternative sources and also from standardised sources

STATE OF THE ART

Burners for combustion of low calorific fuels has to be designed to beable to cope with variable parameters of fuel. Composition of fuelvaries according to the process from which it comes and how it wasobtained. In fuel various incombustible components can occur, most oftenthese are carbon dioxide especially by biofuels or nitrogen, which getsinto fuel generally during fuelification of solids by the air. Exceptthe instable concentration of inert substances also the composition ofcombustible components can fluctuate, mostly methane, hydrogen, carbonmonoxide. The properties of methane, hydrogen, and carbon monoxide aresignificantly different. They have different weight, calorific value,and also combustion velocity.

The combustion velocity is absolutely crucial and has to be consideredby designing of the burner. Simultaneously, the construction has to bedesigned so, that it is possible to satisfy various operatingconditions. For ignition of the burner natural fuel is often used, whichhas significantly higher calorific value than low calorific fuels. Oneof the requirements of the operator used to be also the possibility ofpower regulation within certain range. Therefore, the designer has totake into consideration the fuel flow rate and air velocity and suggesta solution to avoid disruption of flame and its flashback. It isdifficult to keep these parameters.

There exist many solutions, which approach the matter in different ways.Usually, the fuel is supplied by central tube, to which furthertechnical elements are attached. These may be various types of whirlersor parts which ensure mixing of individual components, it means fuel andcombustion air. The solutions according to prior art utilise the insteps supply of the fuel or air and solve the distribution and mixing ofindividual flows in different ways.

In the document EP 0 487 700 B1, so called matrix burner with a burnerhead specially designed for combustion of low calorific fuels, isdescribed. In the middle of the assembly a fuel supply tube on which theentire head is fixed, is located. The head is composed of two steelsheets which are compressed together. The burner head is on the sheetsprovided with matrix arrangement openings, where each opening acts as anindividual small burner. The fuel is then directly mixed with combustionair to form a turbulent flow.

The burner described in the document US2016238241 (A1) is intended tocombustion of lean fuel, it means low calorific fuel (for examplesynthetic fuel resulting from the fuelification of biomass). Theconstruction of the burner utilizes two-stage air supply to achieveenlargement of the flame and a favourable distribution of temperaturefield. The burner is provided with central fuel supply, into whichquality fuel through four openings can be mixed in order to increasecalorific value or for support of the stability. With the expandingburner on the output, the combustion air is gradually blended into theflame.

In the document WO2014204333 (A1) a burner for flaring which is intendedto thermal liquidation of waste fuels (e.g. methane with a high amountof carbon dioxide) without utilization of their energy, is described.The supply pipe is extended twice and on the output from the flare, awhirler is disposed, in order to set the fuel into motion and to achieveturbulent flow. At the end, in the center a cone is inserted, whichdirects the fuel towards the whirler. Behind the cone the fuelcirculates toward the axis of the burner and due to this better mixingis achieved.

The device described in US2008299506 (A1) is a metallurgical burnerprimarily designed for burning of low calorific fuels. The burner has acentral pipe for air supply, around which a fuel supply pipe isarranged. From outer direction secondary air is fed, so that all thefuel is burnt out. Into the fuel flow a whirler creating turbulant flowis placed. It is possible to modify the whirler according to used fuel,especially according to its calorific value.

The document WO2007012755 (A1) describes symmetric burner. Along thecentral axis individual flows of substances are gradually fed. Throughthe central tube fuel is supplied, from which a part is separated, andbefore burning is mixed with the air in a special chamber. A perforatedwhirler which has conical shape is placed at the end of the centraltube, in order to put the fuel into direction. Premixed mixture flowsfrom the chamber through nozzles directly to burning flame. Secondaryair is fed from the outside end using whirling element is directed toachieve its rotation and mixing,

The document EP 1 436 546 discloses a burner which utilises theco-stream arrangement of the fuel and the air. The feature of the burneris a conical extension ending with circular array of nozzles which aredirected to the central surface. Several types of assembly geometry withdifferent mixing ratios and different influence on turbulent flow areproposed.

The aim of the invention is to present a burner assembly for lowcalorific fuels which would ensure sufficient stability of the flame andwhich would also eliminate undesired critical conditions arising duringits operation when disruption of the flame or fire penetration into theburner body occurrs.

SUMMARY OF THE INVENTION

The above mentioned deficiencies are eliminated by the burner head forlow calorific fuels according to the invention, which is characterizedby the fact that in the front face of the central burner tube, a supporttube is fixed, is fixed, on which a burner head (4) at the burner'soutput is mounted, the burner head is provided with nozzles arranged ina circle near to the inner perimeter of the burner head and forming theprimary stage of the burner, and further the burner head is providedwith angled grooves on the outer perimeter, which form the secondarystage of the burner, and further the whirler with its inner perimeter isarranged onto central burner tube at its outlet end and the whirler'ssurface has conical geometry extending outwardly and the whirler'ssurface openings arranged in a circle are provided.

In a preferred embodiment are the openings on the whirler arranged inthree concentric circular rows.

In another preferred embodiment is the fuel supply pipe provided on thewall with weld-on sleeve for connection of the pressure gauge or othermeasuring device.

In another preferred embodiment are on the free end of the support tubescrews for aretation of added atomiser located.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be further described using drawings, where

FIG. 1 is a longitudinal cross-section of built-in burner assemblyaccording to the invention with arrangement of individual parts,

FIG. 2 represents side view of the burner according to the invention inthe direction of media flow,

FIG. 3 represents a detail of the burner head in a perspective view and

FIG. 4 represents a detail of the whirler of combustion air according tothe invention in a perspective view.

PREFERRED EMBODIMENTS OF THE INVENTION

In FIG. 1 a longitudinal section of built-in burner assembly can beseen, which consists of a fuel supply pipe 8 provided with connectingflange 10, through which the fuel F enters in the direction of thearrow. Further is the fuel supply pipe 8 attached to a central burnertube 5 which has a front face 6 on the side of the supply pipe 8, whichhas an opening in the middle to allow insertion of a support tube 7. Thewhole burner is not displayed, only its built-in assembly. Around itthere are situated other standard parts of the burner, which are knownto skilled persons. To the central burner tube 5, at its output end is,via weld-on reduction 3, with its inner perimeter 15 a whirler 2attached. The central burner tube 5 and the weld-on reduction 3, whichterminates the central burner tube 5, form together with the supporttube 7 an assembly, which defines the flow of combustion fuel F. Thus,the fuel F flows in the direction of the arrow into space, which has ashape of a hollow cylinder, formed by the central burner tube 5 and thesupport tube 7. This cylindrical space has such a specific length, sothat the previous turbulent flow is maximally stabilised. Thestabilisation contributes to the uniform distribution of the fuel insidethe cylindrical space and the fuel is then uniformly burnt out. Thesupport tube 7 can be used for addition of an atomiser (not shown) forliquid fuel. At the free end of the support tube 7, screws 12 forarctation of such atomiser are situated. At the opposite inner end ofthe support tube 7 a groove on the burner output is milled into which aburner head 4 is inserted and welded-on, through which the fuel isdistributed into combustion space.

On the wall of the fuel supply pipe 8 a weld-on sleeve 11 is located forconnection of pressure gauge or other measuring device, which can beseen in FIG. 2. On the connecting flange 10 a shutter is possible toinsert in order to regulate pressure on the desired level.

In FIG. 3 the burner head 4 in perspective view is shown. The fuel Fflowing through the burner head 4 via nozzles 13, which are spaced in acircle at the inner perimeter forming the primary stage of the burner 1,is distributed uniformly along the central axis of the burner 1. Thisflow is important especially for the flame core stabilisation. In astable situation in the flame core the flame envelope can be provided ina high rotational mode without disruption of the flame or unstablecombustion. Burner head 4 is at its outer perimeter further providedwith angled grooves 14, which change the momentum direction of flowingfuel and form the secondary stage of the burner 1. The fuel gets afterpassing through the angled grooves 14 into tangential rotation along thecentral axis of the burner 1. Rotational flow causes better mixing ofthe fuel with the combustion air A, which arrives to the end of centralburner tube 5 and simultaneously the flame is partially attached to theburner head 4.

In FIG. 4 whirler 2 in perspective view is shown, its wall 16 hasconical geometry extending outwardly from the burner, which has apositive effect on the flow. In the illustrated embodiment, there areopenings 9 spaced in three concentric circular rows on the wall 16 ofthe whirler 2, through which the combustion air flows. It is evident,that the circle with openings may be only one or there can be anothernumber of concentric circles. After passage through the individualopenings 9 there is a change in the air flow, namely the strongturbulent flow is created, due to which is the fuel brought into atangential rotation and mixed with the combustion air even better. Theangle of inclination of the wall 16 of the whirler 2 has an importantrole, since due to this inclination it is possible to direct partiallythe airflow, to direct it towards the centre of the flame, and causing acomplete combustion.

The burner head 4 has defined number of nozzles 13 arranged in a circle,whereas the number and size of nozzles 13 is determined based on therequirements for maximum performance, according to which the dimensionsare determined so, that the requested amount of fuel flows through theprimary stage created in this way. The number, width, and depth ofangled grooves 14 are determined as to allow the remaining fuel to flowthrough these grooves at maximum power and the groove 14 inclinationangle is determined relative to the plane of the burner head 4 in such away, to ensure optimal turbulent flow in a tangential direction.

INDUSTRIAL APPLICABILITY

The burner is intended for combustion of different types of lowcalorific fuels, also from other alternative devices, such asfuelifiers. Built-in burner assembly is applicable in plants, wherewaste fuels occurs, whose energy is let unused in burners with flaringand flue gases are emitted without use into the atmosphere. Another areawhere it is possible to use the burner, are biogas plants and heatsources connected thereto.

1. The burner, which comprising an air supply pipe, fuel supply pipeattached to a central burner tube, which is terminated by the front faceon the side of the supply pipe, characterized in, that in the front face(6) a support tube (7) is fixed, on which a burner head (4) at theburner's output is mounted, the burner head (4) is provided with nozzles(13) arranged in a circle near to the inner perimeter of the burner head(4) and forming the primary stage of the burner (1), and further theburner head (4) is provided with angled grooves (14) on the outerperimeter, which form the secondary stage of the burner (1), and furtherthe whirler (2) with its inner perimeter (15) is arranged onto centralburner tube (5) at its outlet end, and the whirler's surface (16) hasconical shape extending outwardly and the whirler's surface (16)openings (9), arranged in a circle are provided.
 2. The burner accordingto claim 1, characterized in, that the openings (9) on the whirler (2)are arranged in three concentric circular rows.
 3. The burner accordingto claim 1, characterized in, that the fuel supply pipe (8) is providedon the wall with weld-on sleeve (11) for connection of the pressuregauge or other measuring device.
 4. The burner according to claim 1characterized in, that on the free end of the support tube (7) screws(12) for aretation of added atomiser are located